The present invention relates to novel cycloalkyl-benzopyrans and derivatives thereof, compositions containing those compounds, their use as selective estrogen receptor-beta agonists, and their use in the treatment of estrogen receptor-beta mediated diseases such as prostate cancer, benign prostatic hyperplasia, testicular cancer, ovarian cancer, lung cancer, cardiovascular diseases, neurodegenerative disorders, urinary incontinence, central nervous system (CNS) disorders, gastrointestinal (GI) tract disorders, and osteoporosis.
Estrogens play important roles in the development and homeostasis of the reproductive, central nervous, skeletal, and cardiovascular systems of both males and females. The estrogen receptor (ER) is currently the only member of the steroid subfamily of nuclear receptors that has different subtypes. Recently, a new ER isoform, ER-beta (also known as ER-beta1) was cloned from a rat prostatic cDNA library and is present in murine and human prostates. Consequently, the previous ER is now designated as ER-alpha. ER-alpha and ER-beta share high amino acid homology, have similar 17-β Estradiol (E2) binding affinities, and can hetero- or homodimerize to form a signaling complex; Kuiper G G, et al., Endocrinol. 138: 863–70 (1997); Kuiper G G et al., Proc. Natl. Acad. Sci. USA 93: 5925–30 (1996). Although E2 activates both ER-alpha and ER-beta, ER-alpha stimulates transcription and cellular proliferation, while ER-beta suppresses ER-alpha activation. Interestingly, 3-beta, 17-beta-androstanediol and 5-alpha-androstane have been proposed to be endogenous ligands for ER-beta; Weihua Z. et al. PNAS 98: 6330–5 (2001). 3-Beta, 17-beta-androstanediol is a major metabolite of dihydrotestosterone (DHT), the 5-alpha-reduced active intracellular androgen in male accessory sex organs. ER-beta activation also stimulates increased glutathione S-transferase and quinone reductase expression. These two enzymes have been shown to possess chemoprotective detoxification properties; Chang W Y et al., Prostate 40: 115–24 (1999); Montano M M et al., J. Biol. Chem. 273: 25443–9 (1998).
With the recent identification of ER-beta, and the recognition that ER-alpha and ER-beta have different biological roles, ER-selective modulators would similarly possess significant clinical utility. Since ER-beta is strongly expressed in a number of tissues including prostate, bladder, ovary, testis, lung, small intestine, vascular endothelium, and various parts of the brain, compounds that selectively modulate ER-beta would be of clinical importance in the treatment of a variety of disease conditions, such as prostate cancer, testicular cancer, ovarian cancer, lung cancer, cardiovascular diseases, neurodegenerative disorders, urinary incontinence, CNS disorders, GI tract disorders, and osteoporosis. Such compounds would have minimal effect on tissues that contain ER-alpha, and thus exhibit different side-effect profiles. Thus, ER-beta agonists will display different therapeutic profiles compared to ER-alpha antagonists or agonists, and would be preferentially beneficial in tissues relying on ER-beta signaling.
The prostate gland produces components that are found in the semen and blood. Some of these are regulatory peptides. The prostate gland comprises stroma and epithelium cells, the latter group consisting of columnar secretory cells and basal non-secretory cells. The proliferation of these basal cells, as well as stroma cells gives rise to benign prostatic hyperplasia (BPH), which is one common prostate disease. BPH is a progressive condition that is characterized by the nodular enlargement of the prostatic tissue resulting in obstruction of the urethra. This results in increased frequency of urination, noncuria, poor urine stream, and hesitation or delay in starting the urine flow. Consequences of BPH can include hypertrophy of bladder smooth muscle, decompensated bladder, and increased incidence of urinary tract infection. The development of BPH is considered to be an inescapable phenomenon for the aging male population. BPH is observed in approximately 70% of males over the age of 70. Drug treatment for BPH currently employs alpha andrenergic antagonists for symptomatic relief or steroid 5-alpha reductase inhibitors to reduce hyperplastic tissue bulk. These approaches are of limited therapeutic benefit.
Mortality due to prostatic cancer when the strategem of watchful waiting is adopted is generally low (9%–15%) in men who have localized tumors. However, these rates pertain to patients with localized disease; they do not necessarily apply to younger men at higher risk. Younger men with stage T1a tumors have a longer projected period of risk than older men with the same stage of the disease and are therefore candidates for a potentially curative treatment. In studies of watchful waiting, the high rates of disease progression (34%–80%) indicate that few clinically evident prostate cancers are dormant.